Pneumatic stapler



D. R. TOBIAS' 3,087,466

. PNEUMATIC STAPLER 2 Sheets-Sheet 1 April 30, 1963 Filed Oct. 9. 1956 m6 WW INVENTOR. Mm onl 3% Darrell R. Tobias April 30, 1963 Filed Oct. 9, 1956 D. R. TOBIAS PNEUMATIC STAPLER 2 Sheets-Sheet 2 Darrell R. Tobias IN VEN TOR.

Mm. BY ym; 15m

United States atent O 3,087,466 PNEUMATIC STAPLER Darrell R. Tobias, Sierra Madre, Califi, assignor, by

mesne assignments, to Bostitch Industrial Stapling Machine Co., East Greenwich, EL, a corporation of Rhode Island Filed Oct. 9, 1956, Ser. No. 614,877 19 Claims. (Cl. 121--21) This invention relates to a power tool and more particularly to a fluid-operated stapler.

An object of the invention is to provide a novel stapler which is portable, lightweight, both rapid and dependable in operation, the stapler being preferably pneumatically operated and having an extremely simplified operating mechanism requiring no springs nor mechanically operated valves, other than the trigger. All tools that are now on the market of which I am aware require springs to neturn the staple applying blade, usually actuated by a piston, to the firing position. Otherwise, the presently available tools require complicated valving mechanisms to serve this purpose.

Accordingly, it is a further object of the present invention to provide a simplified pneumatic stapler wherein simplicity of maintenance and original manufacture is stressed in that there is an exceedingly small number of moving parts when considering the terrific driving power developed by the pneumatic stapler Moreover, it is a further object of the invention to provide a stapler of this type which is capable of accomplishing delicate and sensitive jobs, for example, fastening of paper without tearing, and also the heaviest of jobs upon which stapers are ordinarily expected to perform, for example, driving staples into hard wood. A typical stapler constructed in accordance with the principles of the invention is capable of operation at rates in the order of driving 400 staples per minute into a test body.

A further object of the invention is to provide in a stapler of the type disclosed, or any other type, pneumatic means which retain the staple driving blade and its piston in the poised position, these pneumatic means being preferably mere surface areas of dissimilar dimension on the piston so that there is a resultant force generated upon application of pressure from a common source to these areas, this resultant force being in a direction to push the piston in the previously mentioned poised position until moved by a larger force applied in another direction.

A still further object of the invention and which is complementary to the previously mentioned object is to provide a bypass channel for air under pressure, the bypass channel being under the control of the operator, so that when opened at the will of the operator or in response to a mechanical stimulus, air under pressure is applied to the piston and more particularly is applied to a point near the driving end thereof and is permitted to leak past a small part of the piston and to enter a low pressure cavity wherein the fluid pressure is increased until it is sufficient to overcome the previously mentioned resultant force holding the piston in the poised position, when the piston commences to move axially in its cylinder. As the piston so moves, it has its driving end registered with the bypass channel so that the full force of the pneumatic pressure is appled to the driving end of the piston, whereby it is moved to the downward end of its stroke.

Another object of the invention is to provide a cavity that is under line pressure at all times, as is the piston return means, the cavity under line pressure being preferably formed in the handle of the stapler and being opened to the channel that conducts the air under pressure to the driving end of the piston.

3,087,466 Patented Apr. 30, 1963 These together with other objects and advantages which will become subsequently apparent reside in the (details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a longitudinal sectional view of a pneumatic stapler which is constructed in accordance with the invention, the stapler being in such position that it is prepared to be actuated for driving a staple presented to the foot by the staple magazine;

FIGURE 2 is a fragmentary sectional view of the stapler of FIGURE 1 showing in full line position the piston and staple driving blade partially moved to an end of its stroke and showing in dotted line position the piston at the extremity of its stroke;

FIGURE 3 is a transverse, sectional view taken on the line 3-3 of FIGURE 2;

FIGURE 4 is an exploded perspective view of the staple driving blade and its adjustable means to attach it to the piston;

FIGURE 5 is an enlarged sectional view taken on the line 55 of FIGURE 1 and showing the fluted arrange merit of the valve stem; and

FIGURE 6 is a fragmentary sectional view of a modification of the invention.

In the accompanying drawings there is a stapler 10 which is constructed in accordance with the invention. This stapler comprises a body 1 2 made of lightweight, but strong material, and it is preferred that the body be shaped in the form of a gun. Therefore it has a handle 14 of the pistol grip type, this handle having a pressure cavity 16. Trigger guard 18 extends from the main body part to the pistol grip type handle and provides protection for the trigger 20 which is swung on a pivot 22, the latter being carried by body 12. Air passage 24 is located in the body behind trigger 2.0 and opens into valve chamber 25, the latter accommodating a valve stem assembly 28 that is constructed in accordance with Patent No. 2,659,385. Accordingly, it has a fluted stem 30 with a head at one end 3-2 adapted to be actuated by trigger 20 and a valve element 34 at the opposite end which opens and closes on valve seat 36. The valve is opened by actuation of trigger 20 and closed by pneumatic pressure on the face of valve element 34.

Coupling 38 of a standard type is connected in inlet 39 or 39a in body '12 and both inlets are in registry with cavity 16. The coupling is adapted to connect to a source of pneumatic pressure of any value deemed advisable for the particular job that is to be done by the stapler. It is suggested that a standard pressure gauge be used in conjunction with the source of pneumatic pressure so that exact operating pressures may be maintained at all times.

The forward end of body 12 has nose 40*, which is a standard part, connected thereto. In use of the stapler, the forward end of body 12 will be the lowermost or down end, inasmuch as stapling will ordinarily be from above, although it is to be clearly understood that the stapler is capable of actuation at any angle with similar results. The forward end 40 includes a channel 42 that is welded or otherwise attached to nose cap 44-, the latter being bolted, as at 46, to the lower end of the body 12. A stop collar 48 is in the lower end of cylinder 50 formed in body 12 and is abutted by the flange 44. An ordinary magazine 52, capable of storing a sufiicient supply of staples, is connected to the channel 42 and has means, usually spring biased, for elevating and presenting staples into the passage 54 of channel 52- so that they may be ejected by the staple driving blade 56.

Blade 56 is of such dimension and shape as to fi-t in the passage 54 and has its extremity located therein. The opposite end of the blade 56 is secured to a threaded plug 60, as by being fitted in slot 61 therein and held in place by means of transverse dowel 62. Threaded plug 60 is mounted adjustably in the end of piston 64, this piston being of special shape. It has a smaller diameter end 66 and a larger diameter end 68, each being provided with a circumferential groove and supporting an O-ring. The rings 70 and 71 respectively slide on the inner surfaces of the cylinder 50 and more particularly on the smaller diameter part 72 and the larger diameter part 74 thereof. The smaller diameter part 72 of the cylinder 50 is at the forward end of the body 12, while the larger diameter end is at the opposite end of the body. In view of the dissimilarity of diameters of these parts of the piston, there is a piston chamber 78 formed therebetween, this piston chamber having end walls 79 and 80 respectively which are of dissimilar areas, the wall 79 having a larger area than the wall 80 and thereby providing a greater surface upon which pneumatic pressure may be applied. Accordingly, if the pressure is from a single source, the force on the piston 64 will be in two directions, but there will be a resultant force tending to push the piston in the direction of the larger area, that is, the wall 79. Piston chamber 78 and the dissimilar area Walls 79 and 80 coacting with pneumatic pressure from a single source constitute means to retain the piston 64 in the poised position, that is, at one end of body 12 and prepared to undergo a single cycle of operation.

Cap 84 is bolted or otherwise attached to the upper end of body 12 and has a plug 85 which passes into the large diameter part 74 of the cylinder 58. Gasket 86 seals the end of the body and all of the air conductors therein. Low pressure chamber 88 is formed in that end of the body and is defined by the inner surface of plug 85 and the walls of the recess or cup 89 in the adjacent end of piston 64. This low pressure chamber may be varied in accordance with design requirements by enlarging the plug 85 or slightly altering the depth of cup 89 and, correspondingly, making larger or shortening the plug 85.

Air under pressure entering fitting 38 fills cavity 16 and maintains this cavity under line pressure. A channel 90, formed in the body 12 and extending from fitting 38 to annular groove 92 in cylinder 58, constitutes an air conductor and is maintained under line pressure. This means that piston chamber 78 is also under line pressure at all times inasmuch as the piston chamber is in registry with groove 92 and the groove 92 is in direct communication with channel 90. Therefore, piston 64 is retained in the poised position at all times that the pressure is applied from the source.

An annular jacket 95 is formed in the body 12 and is concentric with the larger end of cylinder 50. Generally annular orifice 96 is in registry with the jacket 95 and the larger diameter part of cylinder 50. An annular groove 97 is in the larger part 68 of piston 64, and when the piston is in the poised position (FIGURE 1), the annular groove 97 registers with the annular orifice 96. A bypass conductor 98 has one end in registry with jacket 95 and the other end in registry with valve chamber 26. Accordingly, when the valve is opened, air under line pressure enters conductor 98, annular jacket 95, orifice 96, and groove 97.

It would appear that the piston would not move under these conditions. However, low pressure air is bled past the inner part 100 of the piston 64 and enters the chamber 88. If found necessary or desirable, an orifice may be provided in the part 100 of the piston 64. However, at the present time, successful operation is achieved without resorting to this expedient. As the low pressure increases in chamber 88, the resultant force obtained by algebraically adding the pressures on areas of walls 80 and 79 is overcome, thereby sliding the piston 64 forward in its cylinder. Note that when the valve 34 is opened, not only A is there line pressure applied to conductor 98, but also the pressure of cavity 16 passes through the conductor 98.

As the piston progresses forwardly in the manner described, it reaches a point where the orifice 96 conducts air under pressure to the back part of the piston 64, at which time the piston moves exceedingly fast in a forward direction, since substantially the full line pressure is applied in such manner as to cause piston motion in the forward direction. During this motion blade 56 drives a staple from the foot 40. For countersinking or other operation which require driving the staples beyond the surface of the material being worked with, the length of the blade 56 is altered by merely adjusting the plug 60 in the piston 64.

At the full forward position of the piston, jacket 78 is still in registry with channel 90, and if the trigger 20 is released, permitting line pressure to return the triggeroperated valve assembly to the closed position, the air behind the piston is able to be discharged or exhausted by passing through the jacket and then the conductor 98, then the valve chamber 26, passage 24 through the flutes 188 in the assembly, and to the atmosphere. But, when the trigger 20 is moved to such position to open the valve element 34, close machining of the head 32 or of the shank of the valve assembly and passage 24, the head 32 closes the passage so that no air in any appreciable quantity may escape while valve element 34 is open.

Not only may the air behind the piston 64 be exhausted, but also the piston chamber 78 never becomes disassociated or out of registry with channel 90. Hence, with the removal of the air under pressure from behind the piston, the pneumatic automatic means to return the piston to the poised position become effectual and move the piston to the position shown in FIGURE 1. As an alternate construction (FIGURE 6), the cap 128 has a plug 122 fitting in the larger diameter part 74 of cylinder 50. Passageways 124 controlled by normally closed exhaust check valve 126 connect chamber 88 with jacket 95. This places the exhaust check valve operatively in the system.

In so returning the piston, however, the speed thereof must be arrested, and this is accomplished by utilization of the pressure in the cavity 16 as the piston moves upwardly in body 12. Although the cycle of operation has been described in such manner as to possibly suggest that the steps are accomplished slowly, this is not the case. Upon the first opening of the valve 34 by operation of trigger 20 and the described low pressure leak past the part of piston 64 and into chamber 88, all of the cavities, chambers and the like along the line become equal to the main supply pressure, thereby giving a controlled power drive of the piston. But this is done practically instantaneously. The split second of time interval for chamber 88 to become filled under low pressure provides the time element necessary to accomplish the build-up of equalized, predetermined high pressure in the jacket 95, cavity 16, and other air conducting means in the body being affected at this time.

Although the description has had principal reference to a stapler, it is to be understood that the invention is equally as operable in driving nails or other fasteners. Accordingly, it is not intended that the appended claims be limited to a machine which is exclusively useful with staples.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. In a pneumatic fastener driver that has a body provided with a handle having a cavity, and a cylinder having a larger and a smaller diameter part, a piston having a smaller and a larger diameter part disposed in said smaller and larger parts of said cylinder and a piston chamber separating said parts from each other, a fastener driving blade, means connecting said blade to said piston, an air conductor extending from said handle cavity to said cylinder, said parts of said piston having walls at the ends of said piston chamber that are constantly reacted on by the air under pressure to thereby retain said piston in a rest position, and means in said body to conduct air under pressure from said handle cavity into said cylinder at one end of said piston to drive said piston in said cylinder.

2. A pneumatic fastener driver comprising a body having therein a cavity and a cylinder, said cylinder having portions of different diameters, a piston slidable freely in said cylinder and having portions of different diameters disposed in the corresponding diametered portions of said cylinder, a piston chamber separating said piston portions from each other, a fastener driving member, means connecting said member to said piston, an air conductor extending from said cavity to said cylinder, said piston portions having surfaces at the opposite ends of said piston chamber which are continuously subjected to air under pressure to thereby retain said piston in a rest position, means in said body to conduct air under pressure from said cavity into said cylinder at one end of said piston to drive said piston in said cylinder.

3. In a fastener driver which has a body provided with a cylinder, a piston reciprocable in said cylinder and means connected to said piston to drive a fastener, the improvement comprising means operatively connected with said body and with said piston for retaining the latter in a poised returned position, said piston retaining means including bores in said cylinder of dissimilar size and piston areas of dissimilar size corresponding thereto and respectively slidable therein, an air conductor registered with said cylinder and with a source of compressed air to supply compressed air to both said bores and areas so that the resultant force on said piston tends to move the latter in said cylinder to said poised returned position, and passage means for delivering compressed air from said source to said cylinder and piston for driving the latter from said poised returned position upon its fastener driving stroke, said passage means including means for effecting a relatively slow initial travel of said piston and means for effecting a relatively rapid final travel of said piston during said fastener driving stroke.

4. The combination of claim 3 in which said means for effecting a relatively slow initial travel of said piston and said means for elfecting a relatively rapid final travel of said piston each comprise a continuously open passage free of moving control elements therein.

5. The combination of claim 3 in which said means for effecting a relatively slow initial travel of said piston comprises an open passage free of flow obstructing means and having continuous communication with said cylinder and piston.

6. In a fastener driver which has a body provided with a cylinder, a piston in said cylinder and means connected to said piston to drive a fastener, the improvement comprising means operatively connected with said body and said piston for returning said piston and retaining said piston in a poised, returned position, said piston retaining means consisting of piston areas of dissimilar size, an air conductor to apply air under pressure from a source to both of said areas so that the resultant force on said piston is applied in a manner to tend to move said piston in said cylinder in one direction, a bypass in said body, a pneumatc jacket in said body connected to said bypass, said cylinder having an orifice which intercommunicates said jacket with the interior thereof to enable a part of the air from said jacket to build up behind said piston by leaking past a part of the wall thereof and thereby overcome said resultant force and propel said piston forwardly in said cylinder and when said piston passes said orifice full pneumatic pressure passing through said orifice from the jacket is applied to the piston in a direction to move the piston forwardly within cylinder.

7. In a pneumatic fastener driver, a body having a cylinder with a larger diameter part and a smaller diameter part, a piston in said cylinder with a larger diameter end and a smaller diameter end slidable respectively in said larger and smaller diameter parts of said cylinder, said ends of said piston having a piston chamber therebetween, means for applying pneumatic pressure in said piston chamber so that the resultant force reacting on the piston moves the piston to one end of said cylinder, and delayed means for overcoming said force and driving pneumatically said piston in said cylinder.

8. The combination of claim 7 including means for maintaining a continuous and constant pneumatic pressure in said piston chamber.

9. The combination of claim 8 wherein the last mentioned means has continuous communication with said source of compressed air.

10. In a pneumatic fastener driver, a body having a cylinder with a larger diameter part and a smaller diameter part, a piston in said cylinder with a larger diameter end and a smaller diameter end slidable respectively in said larger and smaller diameter parts of said cylinder, said ends of said piston having a piston chamber therebetween, means for applying pneumatic pressure in said piston chamber so that the resultant force reacting on the piston moves the piston to one end of said cylinder, delayed means for overcoming said force and driving pneumatically said piston in said cylinder, said body having a cavity therein in which to store air under pressure that supplements the source of pneumatic pressure in driving said piston, said cavity also having air under pressure which functions as a cushion during the return of said piston.

11. In a fastener driver which has a body, means to attach a single source of pneumatic pressure thereto, a valve in said body to control pressure from said source, a conductor in said body and exposed to said source of air under pressure at all times and being outside the control of said valve, a cylinder in said body, a piston in said cylinder, said piston having thereon a pair of walls that are spaced from each other and that are of dissimilar area, said conductor being in registry with both of said walls and since said walls are of dissimilar area there is always a resultant force applied to said piston tending to return said piston to an initial position, and means in said body under the control of said valve for applying pressure from said source to said piston to overcome said resultant force.

12. In a fastener driver which has a body, means to attach a single source of pneumatic pressure thereto, a valve in said body to control pressure from said source, a conductor in said body and exposed to said source of air under pressure at all times and being outside the control of said valve, a cylinder in said body, a piston in said cylinder, said piston having thereon a pair of walls that are spaced from each other and that are of dissimilar area, said conductor being in registry with both of said walls and since said walls are of dissimilar area there is always a resultant force applied to said piston tending to return said piston to an initial position, and means in said body under the control of said valve for applying substantially the full pressure of said source to the end of said piston thereby overcoming said resultant force and moving said piston to the opposite end of said cylinder with said resultant force returning said piston to the initial position upon closing said valve.

113. The pneumatic fastener driver of claim 12 wherein the last mentioned means includes an air jacket having an orifice which opens into said cylinder, an air conductor extending from said valve to said air jacket, said piston 2 having a piston ring in said cylinder in advance of said orifice so that air from said jacket under pressure cannot move forwardly in said cylinder but is capable of leaking past said piston in the opposite direction in order to provide a slow pressure build-up behind said piston which moves said piston in said cylinder until the end of said piston passes said orifice whence substantially the full pressure in said jacket is suddenly applied to said piston.

14. In a pneumatic fastener driver having a body and a piston movable in said body together with a blade connected to said piston to drive fasteners delivered successively from a supply thereof, the improvement comprising a pair of spaced dissimilar area walls associated andmovable with said piston, pneumatically operative means connected with a source of pressure and communicating with said piston between said walls for returning said piston to and retaining said piston in an initial position, pneumatic means connected with said source of pressure for overcoming said piston retaining means whereby said piston may move on a driving stroke, said pneumatic means including a time delay means therein enabling pressure equalization between said source of pressure and said pneumatic means.

15. The combination of claim 14 wherein said pneumatic means includes an air jacket surrounding said cylinder and having an inlet port communicating with the interior of said cylinder intermediate the ends thereof, said piston controlling said port, said piston having an operated surface defining with said cylinder and actuating chamber, said time delay means establishing a continuously open but restricted rate of flow of air from said jacket into said actuating chamber.

16. The combination of claim 1 wherein said last mentioned means includes a port opening into said cylinder and controlled by said piston and uncovered by said piston during its driving stroke whereby upon its return stroke said piston will close said port and be cushioned by air trapped and compressed in said cylinder at said one end of said piston.

17. The combination of claim 1 wherein said last mentioned means includes a port opening into said cylinder and controlled by said piston and uncovered by said piston during its driving stroke whereby upon its return stroke said piston will close said port and be cushioned by air trapped and compressed in said cylinder at said one 3% end of said piston, and means establishing a continuous but restricted connection between said handle cavity and said cylinder at said one end of said piston.

18. In a fluid pressure operated fastener driver, the combination of a body that has a cylinder, a piston in said cylinder, said piston having walls of dissimilar area spaced from each other, means connected with said body for attaching to a source of fluid under pressure, an air conductor registered with said means and opening into said cylinder between said walls of said piston so that pressure from said source maintains said piston in a definite rest position, a passageway in said body, a valve chamber with which said passageway is registered, a valve to control said valve chamber by registering the valve chamber with said source attaching means and by closing said chamber from register therewith, said valve controlling the passage of fluid through said passageway and leaving said air conductor open to source pressure, said cylinder having an opening which is operatively connected with said passageway to admit fluid under pressure into said cylinder and at one end of said piston to overcome the pressure force tending to hold said piston in the rest position and propel said piston in said cylinder.

19. The combination of claim 18 wherein there is a jacket in said body and at least partially surrounding said cylinder, said opening in said cylinder being registered with said jacket, said passageway also registered with said jacket to establish a flow path from said valve chamber to said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 922,530 Shoemaker May 25, 1909 1,595,939 Hukill et al Aug. 10, 1926 1,971,048 Parsons Aug. 21, 1934 2,001,190 Ginter May 14, 1935 2,101,159 Stevens Dec. 7, 1937 2,404,051 Ginter July 16, 1946 2,406,747 Davis Sept. 3, 1946 2,585,940 Juilfs Feb. 19, 1952 2,729,198 Faccow Ian. 3, 1956 2,740,859 Beatty et al Apr. 3, 1956 2,872,901 Goldring et al Feb. 10, 1958 

1. IN A PNEUMATIC FASTENER DRIVER THAT HAS A BODY PROVIDED WITH A HANDLE HAVING A CAVITY, AND A CYLINDER HAVING A LARGER AND A SMALLER DIAMETER PART, A PISTON HAVING A SMALLER AND A LARGER DIAMETER PART DISPOSED IN SAID SMALLER AND LARGER PARTS OF SAID CYLINDER AND A PISTON CHAMBER SEPARATING SAID PARTS FROM EACH OTHER, A FASTENER DRIVING BLADE, MEANS CONNECTING SAID BLADE TO SAID PISTON, AN AIR CONDUCTOR EXTENDING FROM SAID HANDLE CAVITY TO SAID CYLINDER, SAID PARTS OF SAID PISTON HAVING WALLS AT THE ENDS OF SAID PISTON CHAMBER THAT ARE CONSTANTLY REACTED ON BY THE AIR UNDER PRESSURE TO THEREBY RETAIN SAID PISTON 